THERMAL CONDUCTIVITY OF LIQUIDS MEASURED WITH THE TRANSIENT HOT-WIRE TECHNIQUE
The accurate knowledge of the thermophysical properties of fluids is crucial for the design and operation of heat transfer equipment. Discrepancies in thermophysical measurements from different laboratories and measurement techniques led the industrial research and development laboratories to search for commercial thermophysical properties instruments that would provide accurate and consistent measurements. One such instrument is the Transient Hot Wire. The Transient Hot-Wire Technique has a well-developed theory that is used to accurately measure the thermal conductivity of liquids, pastes and powders over a wide temperature and pressure range. In
this work three commercial devices, laboratory and portable, are presented. All devices follow the ASTM D7896-19 standard for the thermal conductivity measurements by the Transient Hot-Wire technique. Depending on the model, they differ in the allowable temperature and pressure ranges. The accuracy and repeatability of each instrument were determined by measuring the properties of water, ethylene glycol, heptane, and glycerol at different temperatures. Data taken on all four fluids across all the sensors used had accuracies better than ± 5 %
and repeatability better than ± 1 %, which makes the Transient Hot-Wire a reliable instrument that would provide consistent and accurate results.